This invention relates generally to a pneumatic (compressed-air-operated) reciprocating motor, more particularly to pumping apparatus incorporating the motor and especially to a compressed-air-operated grease gun including the motor for pumping grease.
In one embodiment, the invention involves a grease gun of the type disclosed in the co-assigned U.S. Pat. No. 5,779,105, issued Jul. 14, 1998, entitled Air Operated Grease Gun (xe2x80x9cthe ""105 patentxe2x80x9d), having been developed as an improvement on the commercial version of the gun disclosed in the ""105 patent. While the latter gun has been generally satisfactory, it is subject to shortened life, necessitating early repair of its motor, due to impact involved in operation of the motor. Further, the plunger of the motor has a tendency to jam on occasion.
Accordingly, among the several objects of the invention may be noted the provision of a pneumatic grease gun, i.e., a compressed-air-operated grease gun and a pneumatic (compressed-air-operated) reciprocating motor used in the gun having a longer useful life (without repair) than the gun of the ""105 patent (its predecessor); the provision of pump apparatus used in the gun having a reciprocating pump plunger less subject to jamming than that of the predecessor; and the provision of a gun which is relatively lighter in weight, less noisy in operation, and more economical to manufacture than its predecessor.
In general, the pneumatic reciprocating motor of the invention comprises a motor cylinder having a head end and a rod end, and a motor piston reciprocable in the cylinder having a forward and a back side. The motor piston is reciprocable through a forward stroke toward the rod end of the cylinder and a return stroke back toward the head end and is biased to return back through a return stroke. A piston rod extends forward from the motor piston through the rod end of the cylinder and is reciprocable by the motor piston. The cylinder has an air inlet for admission of compressed air thereto on the back side of the motor piston for driving it forward through a forward stroke against the return bias and an air outlet on the forward side of the motor piston for venting air. The motor piston has through passaging extending from its forward side to its back side, and a valve movable therein relative thereto between a position blocking said through passaging and a position unblocking said through passaging. The cylinder and motor piston have auxiliary passaging for delivery of air under pressure from the back side of the motor piston to move the valve to its said through-passaging-unblocking position at the conclusion of a forward stroke of the motor piston, the motor piston acting as a valve and opening the auxiliary passaging at the conclusion of the forward stroke of the motor piston.
In general, the present invention is also directed to pumping apparatus comprising a motor as outlined in the preceding paragraph with the piston rod thereof constituting the plunger of the pump. A grease gun of this invention comprises the pumping apparatus for pumping grease from a grease supply container appended thereto.
Other objects and features will be in part apparent and in part pointed out hereinafter.